Last updated: August 3, 2026
Almirall, LLC v. Amneal Pharmaceuticals LLC was an ANDA patent case in the U.S. District Court for the District of Delaware concerning Amneal’s proposed generic version of Aczone 7.5% dapsone topical gel. Almirall asserted patents covering dapsone formulations and methods of treating acne. The case ended before trial through a confidential settlement and dismissal. The public record does not disclose the commercial launch date granted to Amneal.
What drug and ANDA were at issue in Almirall v. Amneal?
The dispute involved Aczone 7.5% Gel, whose active ingredient is dapsone. Aczone is a prescription topical treatment for acne vulgaris.
| Item |
Information |
| Branded product |
Aczone 7.5% Gel |
| Active ingredient |
Dapsone |
| Dosage form |
Topical gel |
| Therapeutic category |
Dermatology, acne |
| Brand holder and plaintiff |
Almirall, LLC |
| Generic defendant |
Amneal Pharmaceuticals LLC |
| Regulatory pathway |
Abbreviated New Drug Application |
| Court |
U.S. District Court for the District of Delaware |
| Civil action |
No. 1:19-cv-00658 |
| Filing date |
April 9, 2019 |
| Litigation type |
Hatch-Waxman patent infringement action |
The complaint followed Amneal’s filing of an ANDA and a Paragraph IV certification challenging patents listed for Aczone in the FDA’s Orange Book. Under the Hatch-Waxman Act, the filing of the lawsuit triggered a 30-month stay of FDA approval, subject to statutory exceptions. The case was resolved before a public trial on infringement or validity.
What patents did Almirall assert against Amneal?
Almirall asserted patents directed to topical dapsone formulations and acne-treatment methods. Public case materials identify U.S. Patent Nos. 9,241,946 and 9,517,219 among the patents at issue.
| Patent |
General subject matter |
Relevance to Aczone |
| U.S. Patent No. 9,241,946 |
Topical dapsone formulation and pharmaceutical composition technology |
Formulation protection |
| U.S. Patent No. 9,517,219 |
Methods involving topical dapsone treatment |
Method-of-use protection |
The patents were important because a generic applicant could challenge the listed patents without copying the brand’s trade name or packaging. A successful Paragraph IV challenge could have led to earlier approval and, depending on the product and competitive circumstances, an earlier generic launch.
The asserted claims likely created two different litigation issues:
- Whether Amneal’s proposed formulation fell within the scope of the formulation claims.
- Whether Amneal’s proposed labeling would induce infringement of method-of-use claims directed to acne treatment.
The public docket does not show a judicial decision invalidating either patent or finding infringement after trial. The settlement therefore provides no merits ruling that can be used to measure the court’s view of patent validity, claim construction, or infringement.
What was the litigation timeline?
| Date |
Event |
| April 9, 2019 |
Almirall filed the complaint in the District of Delaware. |
| 2019 |
Amneal responded to the Paragraph IV allegations and defended against the asserted patents. |
| 2019-2020 |
The parties proceeded through Hatch-Waxman litigation and settlement discussions. |
| Before trial |
The action was resolved through a confidential settlement. |
| After settlement |
The case was dismissed, with no published merits judgment. |
The case number, 1:19-cv-00658, identifies the Delaware action. It should not be confused with separate Almirall patent suits involving other dermatology products, including tazarotene, clindamycin/tretinoin, or other products acquired or commercialized by Almirall.
What was the settlement agreement between Almirall and Amneal?
The settlement terms were confidential. Public docket materials indicate that the case ended without a reported trial verdict or patent-invalidity judgment.
The public record therefore does not establish:
- Amneal’s agreed launch date;
- Whether Amneal received a license to launch before patent expiration;
- Whether launch was contingent on a third-party generic entrant;
- Whether the agreement included a volume restriction, authorized-generic arrangement, or other commercial provision;
- Whether Almirall agreed to withdraw or amend any Orange Book listing;
- Whether Amneal was required to maintain a particular label or carve out a patented indication.
In pharmaceutical patent analysis, a confidential settlement should not be treated as a confirmation that the asserted patents were valid and infringed. It also should not be treated as evidence that Amneal’s Paragraph IV position was legally correct. The settlement removed the need for the court to decide those questions.
What was the Orange Book status of Aczone?
Aczone’s Orange Book position was based on patents associated with the approved dapsone topical gel product. Orange Book listings can include formulation patents, method-of-use patents, or both.
For a generic applicant, the principal regulatory consequences were:
- A Paragraph IV certification could trigger patent litigation.
- The lawsuit could impose a 30-month approval stay.
- FDA approval could proceed after the stay unless another legal barrier applied.
- A successful first-filer could potentially receive 180 days of generic exclusivity, subject to forfeiture and other statutory rules.
The Orange Book listing alone does not establish that every listed patent would survive invalidity review. Nor does a confidential settlement establish the exact relationship between the patent expiry dates and any agreed generic entry date.
When does Aczone lose patent exclusivity?
The principal patent term dates depend on the specific patent and any applicable patent-term adjustment or extension. U.S. Patent No. 9,241,946 has a patent term extending into the 2020s, while U.S. Patent No. 9,517,219 has a later expiration date because it claims priority to a later patent family.
The relevant distinction is between:
- the expiration of an earlier formulation patent;
- the expiration of a later method-of-use patent;
- FDA regulatory exclusivity;
- and any private launch restriction created by settlement.
A generic company may obtain FDA approval after the 30-month stay but still face commercial limits under a settlement. Conversely, a settlement may permit launch before the latest listed patent expires. The case docket does not publicly disclose the contractual date that controlled Amneal’s launch.
FDA exclusivity is separate from patent protection. Aczone did not receive biologic exclusivity, and biosimilar rules do not apply because dapsone gel is a small-molecule topical drug.
How strong was Almirall’s Aczone patent estate?
Almirall’s Aczone estate had meaningful commercial value because it combined formulation and method-of-use claims. Formulation claims can be difficult to design around when the product requires a particular concentration, vehicle, particle-size distribution, or delivery system. Method claims can be more vulnerable if a generic applicant can use a narrower label or omit a patented indication.
The estate’s practical strength depended on four issues:
Formulation claim scope
A formulation patent has greater blocking value when the claims capture the commercially necessary composition rather than optional excipients. If a generic can alter the vehicle while preserving therapeutic performance, design-around risk increases.
Label-induced infringement
Method-of-use claims can create a substantial risk where the generic label directs use for the patented indication. A skinny-label strategy may reduce that risk if the patented use can be cleanly removed without undermining approval.
Patent-term separation
Later-expiring method patents can preserve leverage after an earlier formulation patent expires. Their value depends on whether the approved label and ordinary physician use make infringement likely.
Litigation economics
A settlement can preserve the brand’s price and delay generic erosion, but its economic value depends on the agreed entry date. A launch close to formulation-patent expiry can produce a materially different outcome from an entry date tied to a later method patent.
Because the case ended without a claim-construction opinion or trial judgment, the public record does not provide a court-tested measure of claim strength.
What generic entry risks existed for Almirall?
The principal risk was an Amneal launch following settlement rather than an immediate loss at trial. The expected exposure included:
- rapid price erosion after generic entry;
- pharmacy substitution for topical dapsone gel;
- loss of market share among acne patients with prescription coverage;
- pressure on payer reimbursement;
- competitive entry by additional ANDA applicants;
- possible erosion of branded Aczone revenue before the expiry of all listed patents.
Topical dermatology products can experience meaningful erosion even when substitution is less automatic than with oral solid dosage forms. Formulary placement, prescriber loyalty, patient response, and product availability influence the speed of conversion.
The case also had a follow-on risk: once one generic company establishes an approved product and a launch date, other ANDA applicants may enter under separate settlements or after later patent expirations.
Which companies were challenging Aczone?
Amneal was the defendant in this action. The public case record establishes Amneal’s ANDA challenge but does not, by itself, establish the complete universe of companies that may have filed separate ANDAs or Paragraph IV certifications for Aczone.
A company-specific patent case should not be used as a complete market census. The FDA Orange Book identifies listed patents, while FDA approval records and individual district-court complaints identify particular ANDA applicants.
What was the FDA status of the generic product?
The litigation indicates that Amneal had submitted an ANDA containing a Paragraph IV certification. That filing does not establish final FDA approval. FDA approval and commercial launch are separate events.
The public litigation record does not provide a confirmed Amneal approval date or commercial launch date. It also does not establish whether the FDA approved the application after the statutory stay, whether approval was tentatively granted, or whether any approval was delayed for reasons unrelated to patent litigation.
Did the case involve licensing, biosimilars, or manufacturing patents?
The case was a small-molecule Hatch-Waxman dispute. It did not involve biosimilar interchangeability, the Biologics Price Competition and Innovation Act, or biologic patent dance procedures.
The public case materials do not identify a manufacturing-process patent as the central asserted right. The commercial dispute focused on the approved topical formulation and acne-treatment methods. No public record establishes a technology license outside the confidential settlement.
What is the commercial significance of the case?
The case protected Almirall’s position in the U.S. acne market by avoiding a public invalidity or noninfringement judgment. Its principal commercial value was the ability to negotiate generic timing while preserving control over the Aczone patent estate.
For Amneal, the case created a pathway to potential market entry without the cost and uncertainty of a full patent trial. The value of that pathway depended on the settlement date, the remaining patent term, FDA approval timing, and the number of competing generic applicants.
The lawsuit’s outcome should therefore be modeled as a confidential-entry settlement, not as a patent win or loss. Revenue forecasting requires the actual launch provision, which is not public in the docket.
Key Takeaways
- Almirall sued Amneal in Delaware on April 9, 2019, over an ANDA for generic Aczone 7.5% dapsone gel.
- The case involved formulation and method-of-use patent claims, including U.S. Patent Nos. 9,241,946 and 9,517,219.
- The litigation ended through a confidential settlement before a public merits ruling.
- The public record does not disclose Amneal’s agreed launch date or commercial settlement terms.
- The dispute involved a small-molecule generic, not a biosimilar.
- Almirall retained settlement leverage because the Aczone estate covered both the product formulation and acne-treatment methods.
- The case does not establish that the asserted patents were valid and infringed, because no trial judgment was entered.
FAQs About Almirall v. Amneal
Was Almirall v. Amneal an ANDA Paragraph IV case?
Yes. The action followed Amneal’s Paragraph IV challenge to patents listed for Aczone 7.5% dapsone gel.
Did Amneal win the Aczone patent litigation?
No public merits judgment awarded victory to either party. The case was resolved by confidential settlement and dismissed.
What product was protected by the patents in the case?
The product was Aczone 7.5% Gel, a topical dapsone product approved for acne vulgaris.
Is Amneal’s Aczone launch date public?
The public docket does not disclose a definitive commercial launch date under the settlement.
Can the case be used to predict generic entry for other Almirall dermatology products?
Only with caution. The case concerns Aczone and its specific patent family. It does not establish the settlement terms, patent strength, or launch timing for Almirall’s other dermatology products.
References
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Almirall, LLC v. Amneal Pharmaceuticals LLC, No. 1:19-cv-00658 (D. Del. filed Apr. 9, 2019). U.S. District Court for the District of Delaware docket.
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U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.
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U.S. Patent and Trademark Office. (2016). U.S. Patent No. 9,241,946: Topical pharmaceutical compositions. Washington, DC: U.S. Department of Commerce.
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U.S. Patent and Trademark Office. (2016). U.S. Patent No. 9,517,219: Methods of treating acne. Washington, DC: U.S. Department of Commerce.
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U.S. Food and Drug Administration. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, 21 U.S.C. § 355(j).
